I have been trying all morning to find the right Ubuntu Server (12.04) ISO to use for installing an Ubuntu guest OS on my VBox VM.

Here are the relevant stats:

Host Machine: AMD 64-bit

Host OS: Ubuntu Desktop 11.04

VM OS: Linux

VM OS Version: Ubuntu

ISO downloaded and attempted: ubuntu-12.04-server-amd64.iso

When I try to start the VM I get a main menu, the first option reads Install Ubuntu. When I select that, I get an error message:

This kernel requires an x86-64 CPU, but only detected an i686 CPU. Unable to boot - please use a kernel appropriate for your CPU.

Edit: That message makes me think that I have a 32-bit machine but am trying to run a 64-bit ISO. I am confident that this is 64-bit, however, as uname -m produces x86-64 in the terminal...and executing lscpu produces:

Here's the kicker: I downloaded the ISO on a Windows machine, because my Ubuntu machine (the one running Ubuntu Desktop 11.04 and hosting the VM-to-be) has crummy network connection. So I downloaded to a Windows client, put the ISO on a flash drive, copied it over to my Ubuntu machine, and saved it locally. I'm wondering if the download page saw that I was trying to download from a Windows client and swapped out the x86-64 version for i686? Otherwise I downloaded the wrong ISO.

Can someone please tell me what the right ISO is? I thought for sure the AMD 64-bit version would be exactly what I needed.

You must enable hardware virtualization for the particular VM for which you want 64-bit support; software virtualization is not supported for 64-bit VMs.

If you want to use 64-bit guest support on a 32-bit host operating system, you must also select a 64-bit operating system for the particular VM. Since supporting 64 bits on 32-bit hosts incurs additional overhead, VirtualBox only enables this support upon explicit request.

On 64-bit hosts (which typically come with hardware virtualization support), 64-bit guest operating systems are always supported
regardless of settings, so you can simply install a 64-bit operating
system in the guest.

Warning

On any host, you should enable the I/O APIC for virtual machines that
you intend to use in 64-bit mode. This is especially true for 64-bit
Windows VMs. See the section called “"Advanced" tab”. In addition, for
64-bit Windows guests, you should make sure that the VM uses the Intel
networking device, since there is no 64-bit driver support for the AMD
PCNet card; see the section called “Virtual networking hardware”.

If you use the "Create VM" wizard of the VirtualBox graphical user
interface (see the section called “Creating your first virtual
machine”), VirtualBox will automatically use the correct settings for
each selected 64-bit operating system type.

So, just try creating a new Virtual Machine and select Ubuntu 64 as the OS. All the settings should be correctly configured by VirtualBox and you should be able to install with no problems.

@zharvey No, you do not have an AMD processor. You are, however, on an x86_64 architecture. Apple and AMD were the first to come out with a 64bit system for personal computers. So, in the non mac world, amd64 was adopted for all 64bit architectures. x86_64 was later adopted to describe intel 64bit CPUs as well. The two names are essentially synonymous today.
–
terdonAug 21 '12 at 14:35

I don't get the third point "If you want to use 64-bit guest support on a 32-bit host operating system, you must also select a 64-bit operating system for the particular VM". you must also select a 64-bit operating system for the particular VM what do you mean by that ?
–
Suhail GuptaJul 19 '13 at 7:59

@SuhailGupta that just means that you should install a 64bit operating system on your virtual machine.
–
terdonJul 19 '13 at 11:42